He told the US District Court in Washington DC: "I made a awful mistake for which I paid dearly and I am terribly ashamed".

The 31-year-old Chicago-based worldwide energy lawyer admitted that he lied to the Federal Bureau of Investigation in order to cover up interactions he had with Russian operatives about obtaining damaging information about Hillary Clinton.

"The President of the United States hindered this investigation more than George Papadopoulos ever could", Mr Breen said.

Papadopoulos apparently raised the possibility of setting up a meeting between Trump and Putin during a national security meeting in March 2016. The diplomat relayed the information to his government, which passed it along to the USA government.

However, reporting has suggested that he had been more involved with the campaign than the Trump team has let on.

"Caught off-guard by an impromptu interrogation, Mr Papadopoulos misled investigators to save his professional aspirations and preserve a perhaps misguided loyalty to his master", the statement said.

Russian Federation has denied USA allegations that it interfered in the campaign and President Trump denies campaign collusion.

Defense counsel in their filings painted Papadopoulos as a naive and eager campaign aid who sought to impress the Trump campaign by setting up a meeting with campaign officials and Russian Federation to discuss whatever Russian Federation allegedly had on Ms. Clinton.

Papadopoulos acknowledged that he had lied to investigators about contacts with a Kremlin-linked professor who informed him in April 2016 that the Russians had "dirt" on Hillary Clinton and "thousands of emails".

The former Trump aide's legal team has requested leniency, asking that Papadopoulos receive probation but no prison time. "The defendant's lies undermined investigators' ability to challenge the Professor or potentially detain or arrest him while he was still in the United States", they wrote, noting that Mifsud left the U.S.in February 2017 and hasn't returned.

Papadopoulos had told investigators that the conversation happened before he became a Trump campaign adviser, when in fact he had worked for the campaign for more than a month at the time.